Antidiabetic drug metformin alleviates endotoxin-induced fulminant liver injury in mice. Int Immunopharmacol. 2012;12:682-688. [PMID: 22330083 DOI: 10.1016/j.intimp.2012.01.015]

Metformin and the Liver: Unlocking the Full Therapeutic Potential

Metformin is a highly effective medication for managing type 2 diabetes mellitus. Recent studies have shown that it has significant therapeutic benefits in various organ systems, particularly the liver. Although the effects of metformin on metabolic dysfunction-associated steatotic liver disease and metabolic dysfunction-associated steatohepatitis are still being debated, it has positive effects on cirrhosis and anti-tumoral properties, which can help prevent the development of hepatocellular carcinoma. Furthermore, it has been proven to improve insulin resistance and dyslipidaemia, commonly associated with liver diseases. While more studies are needed to fully determine the safety and effectiveness of metformin use in liver diseases, the results are highly promising. Indeed, metformin has a terrific potential for extending its full therapeutic properties beyond its traditional use in managing diabetes.

The anti-inflammatory effect of metformin: The molecular targets

Metformin is an anti-diabetic drug. Metformin mainly inhibits gluconeogenesis in the liver and reduces blood sugar. In addition to the anti-diabetic effects, many studies have revealed that metformin has anti-inflammatory effects. Various molecules were suggested to be the target of the metformin's anti-inflammatory effects. However, the conclusion is not clear. Metformin is related to a number of molecules and the identification of the main target in anti-inflammatory effects leads to the understanding of inflammation and metformin. In this article, I discuss each suggested molecule, involved mechanisms, and their relationship with various diseases.

Metformin inhibits paclitaxel-induced mechanical allodynia by activating opioidergic pathways and reducing cytokines production in the dorsal root ganglia and thalamus

It has been shown that AMP-activated protein kinase (AMPK) is involved in the nociceptive processing. This observation has prompted us to investigate the effects of the AMPK activator metformin on the paclitaxel-induced mechanical allodynia, a well-established model of neuropathic pain. Mechanical allodynia was induced by four intraperitoneal (i.p) injections of paclitaxel (2 mg/kg.day) in mice. Metformin was administered per os (p.o.). Naltrexoneandglibenclamide were used to investigate mechanisms mediating metformin activity. Concentrations of cytokines in the dorsal root ganglia (DRG) and thalamus were determined. After a single p.o. administration, the two highest doses of metformin (500 and 1000 mg/kg) attenuated the mechanical allodynia. This response was attenuated by all doses of metformin (250, 500 and 1000 mg/kg) when two administrations, 2 h apart, were carried out. Naltrexone (5 and 10 mg/kg, i.p.), but not glibenclamide (20 and 40 mg/kg, p.o.), attenuated metformin activity. Concentrations of tumor necrosis factor (TNF)-α, interleukin (IL)-1β and CXCL-1 in the DRG were increased after administration of paclitaxel. Metformin (1000 mg/kg) reduced concentrations of TNF-α, IL-1β and CXCL-1 in the DRG. Concentration of IL-6, but not TNF-α, in the thalamus was increased after administration of paclitaxel. Metformin (1000 mg/kg) reduced concentration of IL-6 in the thalamus. In summary, metformin exhibits activity in the model of neuropathic pain induced by paclitaxel. This activity may be mediated by activation of opioidergic pathways and reduced production of TNF-α, IL-1β and CXCL-1 in the DRG and IL-6 in the thalamus.

Metformin: update on mechanisms of action on liver diseases

Substantial attention has been paid to the various effects of metformin on liver diseases; the liver is the targeted organ where metformin exerts its antihyperglycemic properties. In non-alcoholic fatty liver disease (NAFLD), studies have shown that metformin affects the ATP/AMP ratio to activate AMPK, subsequently governing lipid metabolism. The latest research showed that low-dose metformin targets the lysosomal AMPK pathway to decrease hepatic triglyceride levels through the PEN2-ATP6AP1 axis in an AMP-independent manner. Metformin regulates caspase-3, eukaryotic initiation factor-2a (eIF2a), and insulin receptor substrate-1 (IRS-1) in palmitate-exposed HepG2 cells, alleviating endoplasmic reticulum (ER) stress. Recent observations highlighted the critical association with intestinal flora, as confirmed by the finding that metformin decreased the relative abundance of Bacteroides fragilis while increasing Akkermansia muciniphila and Bifidobacterium bifidum. The suppression of intestinal farnesoid X receptor (FXR) and the elevation of short-chain fatty acids resulted in the upregulation of tight junction protein and the alleviation of hepatic inflammation induced by lipopolysaccharide (LPS). Additionally, metformin delayed the progression of cirrhosis by regulating the activation and proliferation of hepatic stellate cells (HSCs) via the TGF-β1/Smad3 and succinate-GPR91 pathways. In hepatocellular carcinoma (HCC), metformin impeded the cell cycle and enhanced the curative effect of antitumor medications. Moreover, metformin protects against chemical-induced and drug-induced liver injury (DILI) against hepatotoxic drugs. These findings suggest that metformin may have pharmacological efficacy against liver diseases.

Evaluating the protective effect of metformin against diclofenac-induced oxidative stress and hepatic damage: In vitro and in vivo studies

Diclofenac (DIC) is one of the most commonly prescribed non-steroidal anti-inflammatory drugs and has been shown to cause oxidative stress and liver injury. The current study investigated protective effects of metformin against DIC-induced hepatic toxicity in both in vitro and in vivo models. For the in vitro study, HepG2 cells were exposed to DIC in the presence or absence of metformin. The effect of metformin on cell viability was evaluated by MTT assay. Oxidative stress parameters (malondialdehyde (MDA), total thiol molecules (TTM), and total antioxidant capacity (TAC)) were assessed. For the in vivo study, thirty-six male Wistar rats were randomly divided into 6 groups. These groups were normal saline, metformin (200 mg/kg), DIC (50 mg/kg/day), DIC + metformin (50, 100, and 200 mg/kg/day). Histopathological studies and serum levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), lactate dehydrogenase (LDH), albumin, direct and total bilirubin were measured. Also, oxidative stress parameters were assessed in liver tissue. Furthermore, expression of glutathione peroxidase (GPX)-1, -3, and -4, catalase (CAT), superoxide dismutase (SOD)-1, and -3 was examined using the real-time PCR method in hepatic tissue. In the in vitro study, metformin significantly prevented DIC-induced loss in cell viability in HepG2 cells. Metformin markedly reduced DIC-induced elevation of MDA levels and increased the TAC and TTM levels. In the in vivo study, metformin significantly prevented DIC-induced changes in hematological and histological markers. Administration of metformin significantly improved oxidative stress parameters in liver tissue. In addition, metformin increased the expression of antioxidant enzymes. Our results suggest that metformin exerts a significant protective effect against DIC-induced hepatic toxicity.

Metformin pretreatment ameliorates busulfan-induced liver endothelial toxicity during haematopoietic stem cell transplantation

The success of Haematopoietic cell transplantation (HCT) is often limited by regimen-related toxicity (RRT) caused by conditioning regimen drugs. Among different conditioning drugs, busulfan (Bu) and treosulfan (Treo), although widely used in HCT, exhibit different toxicity profiles, the mechanism of which is still unclear. Here we investigated the effects of Bu and Treo in endothelial cells. While both Bu and Treo induced DNA damage in endothelial cells, we observed Bu alone to induce oxidative stress and sustained activation of phospho-ERK1/2, leading to apoptosis. However, Treo-treated cells exhibited no oxidative stress/apoptosis of endothelial cells. Screening of pharmacological inhibitors of both ROS and p-ERK revealed that metformin effectively ameliorates Bu-mediated toxicity in endothelial cells. In Balb/c mice, we observed a significant reduction in bone marrow endothelial cells in Bu-treated mice compared to Treo-treated mice. Further, liver sinusoidal endothelial cells (LSEC) was damaged by Bu, which is implicated in liver vasculature and their functional capacity to uptake FITC-albumin. However, Treo-treated mice liver vasculature was morphologically and functionally normal. When mice were pretreated with metformin followed by Bu, LSECs damage was ameliorated morphologically and functionally. Bone marrow transplants done on these mice did not affect the engraftment of donor cells.

The effects of carvacrol on oxidative stress, inflammation, and liver function indicators in a systemic inflammation model induced by lipopolysaccharide in rats

The effect of carvacrol (CAR) on oxidative stress, inflammation, and liver dysfunction induced by lipopolysaccharide (LPS) was explored. The rats (n=40) were daily injected (2 weeks) by saline as control, LPS (1 mg/kg, i.p.), and 25, 50 or 100 mg/kg CAR (i.p.) before LPS. LPS increased aspartate transaminase (AST: 162±13 U/L), alanine aminotransferase (ALT: 74.6±2.15 U/L), alkaline phosphatase (ALK-P: 811±51 U/L), interlukine-1β (IL-1β: 1254±51 pg/g tissue), malondialdehyde (MDA: 32±1.09 nM/g tissue), and nitric oxide (NO: 224±13.5 nM/g tissue) (P<0.01-P<0.001) while, decreased total protein(4.08±0.38 g/dl), albumin(2.79±0.16 g/dl), thiol (5.16±0.19 μM/g tissue), superoxide dismutase (SOD: 10.57±0.13 U/g tissue), and catalase (CAT: 0.78±0.02 U/g tissue) compared to control (P<0.001). CAR reversed the effects of LPS (P<0.05-P<0.001). In the rats treated by 100 mg/kg CAR, the indicators were as follows: AST: 118±10.1 U/L, ALT: 42.5±4.13 U/L, ALK-P: 597±39.91 U/L, IL-1β: 494±15 pg/g tissue, and NO: 141±5.35 nM/g tissue. Both 50 and 100 mg/kg CAR corrected oxidative stress indicators and in the group treated by 100 mg/kg CAR, they were: MDA: 23.4±0.91 nM/g tissue, thiol: 7.98±0.18 μM/g tissue, SOD: 21±0.8 U/g tissue, and CAT: 1.12±0.02 U/g tissue(P<0.05-P<0.001). In conclusion, CAR improved liver function, accompanied with antioxidant and antiinflammatory effects.

Enhancement of liver mitochondrial complex I and energy metabolism induced by enteritis: The key role of gut microbiota derived endotoxins

Inflammation is an energy-intensive process and the liver is a key organ in energy regulation. Since the intestine and liver exchange nutrients and metabolites, enteritis can affect the liver. To investigate the correlation between enteritis and liver metabolism, we developed an intestinal inflammation model with concentration-dependent 2,4,6-trinitrobenzene sulfonic acid (TNBS) in gibel carp (Carassius gibelio). The results showed the dysregulation of intestinal tight junction, increased permeability of the gut barrier, and apoptosis of epithelial cells during the development of enteritis. The liver metabolome was analyzed by LC-MS and the live respiration was determined using Oxygraph-2k. The results showed that glycolysis, the TCA cycle and pyrimidine metabolism were affected by intestinal inflammation. In particular, the activity of hepatic mitochondrial respiratory chain complex I was significantly increased. Structure and abundance changes of gut microbiota were analyzed by 16S rRNA sequencing analysis. Pathogenic bacteria in the intestine, as well as plasma LPS, increased significantly. Using a liver cell line, we verified that the dysfunctional metabolism of the liver is related to the dislocation of LPS. All results imply the existence of a connection between enteritis and liver metabolism in gibel carp, and the gut microbiome plays a critical role in this process.

Excess DHA Induces Liver Injury via Lipid Peroxidation and Gut Microbiota-Derived Lipopolysaccharide in Zebrafish

Being highly unsaturated, n-3 long-chain polyunsaturated fatty acids (LC-PUFAs) are prone to lipid peroxidation. In this study, zebrafish were fed with low-fat diet (LFD), high-fat diet (HFD), or 2% DHA-supplemented HFD (HFDHA2.0). To study the possible negative effects of the high level of dietary DHA, growth rates, blood chemistry, liver histology, hepatic oxidative stress, apoptosis, and inflammatory processes were assessed. The cell studies were used to quantify the effects of DHA and antioxidant on cellular lipid peroxidation and viability. The possible interaction between gut microbiota and zebrafish host was evaluated in vitro. HFDHA2.0 had no effect on hepatic lipid level but induced liver injury, oxidative stress, and hepatocellular apoptosis, including intrinsic and death receptor-induced apoptosis. Besides, the inclusion of 2% DHA in HFD increased the abundance of Proteobacteria in gut microbiota and serum endotoxin level. In the zebrafish liver cell model, DHA activated intrinsic apoptosis while the antioxidant 4-hydroxy-Tempo (tempo) inhibited the pro-apoptotic negative effects of DHA. The apoptosis induced by lipopolysaccharide (LPS) was unaffected by the addition of tempo. In conclusion, the excess DHA supplementation generates hepatocellular apoptosis-related injury to the liver. The processes might propagate along at least two routes, involving lipid peroxidation and gut microbiota-generated LPS.

Metformin versus Silymarin as Hepatoprotective Agents in Mice Fibrotic Model Caused by Carbon Tetrachloride

OBJECTIVES

To study metformin hepatoprotective effects compared to silymarin on hepatic fibrosis caused by carbon tetrachloride (CCl4) in mice.

MATERIAL AND METHODS

liver fibrosis in mice was achieved by intraperitoneal injection of 2 ml/kg of CCl4 dilution in olive oil [1:9 (v/v)] twice a week for 7 weeks followed by oral treatment with metformin (250 mg/kg/day) or silymarin (100 mg/kg/day) (a standard hepatoprotective drug). The changes that follow liver fibrosis were assessed by measurement of hepatic enzymes (ALT, AST and ALP), histopathological examination using hematoxylin and eosin stain, special stains, and α-smooth muscle actin (α-SMA) immunostaining, measuring oxidative stress markers (MDA, GSH, NOx and MnSOD) and transforming growth factor-beta 1 (TGF-β1) in liver.

RESULTS

liver fibrosis was obviously developed in mice after intraperitoneal injection with CCl4 for 7 weeks. Both silymarin and metformin treatment exhibited a significant decrease in the fibrotic changes and similarly an increase in endogenous antioxidants. Interestingly there is a significant difference between silymarin and metformin regarding both efficacy and potency.

CONCLUSION

These findings highlight the anti-inflammatory, antioxidant and antifibrotic effects of metformin in CCl4-induced hepatic fibrosis in mice, but silymarin is more beneficial.

Metformin effect in models of inflammation is associated with activation of ATP-dependent potassium channels and inhibition of tumor necrosis factor-α production

Metformin is an oral hypoglycemic drug widely used in the management of type 2 diabetes mellitus. We have recently demonstrated that metformin exhibits activity in models of nociceptive and neuropathic pain. However, little is known about its effects in experimental models of inflammation and inflammatory pain. Thus, the present study aimed to evaluate the activity of metformin in experimental models of inflammation and inflammatory pain in mice, as well as the underlying mechanisms. Previous (1 h) per os (p.o.) administration of metformin (250, 500 or 1000 mg/kg) inhibited the mechanical allodynia and paw edema induced by intraplantar (i.pl.) injection of carrageenan (600 μg) and also the pleurisy induced by this stimulus (200 μg, intrapleural). In the model of mechanical allodynia and paw edema induced by carrageenan, metformin also exhibited activity when administered after (1 h) the inflammatory stimulus. Metformin (1000 mg/kg) reduced the production of tumor necrosis factor-α induced by i.pl. injection of carrageenan. Metformin antiallodynic effect was not affected by previous administration of naltrexone (5 or 10 mg/kg, intraperitoneal) or cyproheptadine (5 or 10 mg/kg, p.o). However, this effect was abolished by previous administration of glibenclamide (20 or 40 mg/kg, p.o). In conclusion, the results demonstrate the activity of metformin in models of inflammation and inflammatory pain. In addition, the results indicate that the activity of metformin may be mediated by activation of ATP-sensitive potassium channels and reduction of production of inflammatory mediators. Altogether, these results stimulate the conduction of studies aiming to evaluate whether metformin may be repositioned in the treatment of patients with painful and inflammatory disorders.

Metformin Improves Autonomic Nervous System Imbalance and Metabolic Dysfunction in Monosodium L-Glutamate-Treated Rats

Metformin is an antidiabetic drug used for the treatment of diabetes and metabolic diseases. Imbalance in the autonomic nervous system (ANS) is associated with metabolic diseases. This study aimed to test whether metformin could improve ANS function in obese rats. Obesity was induced by neonatal treatment with monosodium L-glutamate (MSG). During 21-100 days of age, MSG-rats were treated with metformin 250 mg/kg body weight/day or saline solution. Rats were euthanized to evaluate biometric and biochemical parameters. ANS electrical activity was recorded and analyzed. Metformin normalized the hypervagal response in MSG-rats. Glucose-stimulated insulin secretion in isolated pancreatic islets increased in MSG-rats, while the cholinergic response decreased. Metformin treatment normalized the cholinergic response, which involved mostly the M3 muscarinic acetylcholine receptor (M3 mAChR) in pancreatic beta-cells. Protein expression of M3 mAChRs increased in MSG-obesity rats, while metformin treatment decreased the protein expression by 25%. In conclusion, chronic metformin treatment was effective in normalizing ANS activity and alleviating obesity in MSG-rats.

Metformin Modulates T Cell Function and Alleviates Liver Injury Through Bioenergetic Regulation in Viral Hepatitis

Metformin is not only the first-line medication for the treatment of type 2 diabetes, but it is also effective as an anti-inflammatory, anti-oxidative and anti-tumor agent. However, the effect of metformin during viral hepatitis remains elusive. Using an adenovirus (Ad)-induced viral hepatitis mouse model, we found that metformin treatment significantly attenuated liver injury, with reduced serum aspartate transaminase (AST) and alanine transaminase (ALT) levels and liver histological changes, presumably via decreased effector T cell responses. We then demonstrated that metformin reduced mTORC1 activity in T cells from infected mice, as evidenced by decreased phosphorylation of ribosome protein S6 (p-S6). The inhibitory effects on the mTORC1 signaling by metformin was dependent on the tuberous sclerosis complex 1 (TSC1). Mechanistically, metformin treatment modulated the phosphorylation of dynamin-related protein 1 (Drp-1) and mitochondrial fission 1 protein (FIS1), resulting in increased mass in effector T cells. Moreover, metformin treatment promoted mitochondrial superoxide production, which can inhibit excessive T cell activation in viral hepatitis. Together, our results revealed a protective role and therapeutic potential of metformin against liver injury in acute viral hepatitis via modulating effector T cell activation via regulating the mTORC1 pathway and mitochondrial functions.

Concerted outcome of metformin and low dose of radiation in modulation of cisplatin induced uremic encephalopathy via renal and neural preservation

AIM

The therapeutic expediency of cisplatin was limited due to its nephrotoxic side effects, so this study planned to assess the nephrotic and neuroprotective impact of metformin (MET) and low-dose radiation (LDR) in cisplatin-prompted kidney injury and uremic encephalopathy (UE).

METHODS

The effect of the 10-day MET treatment (200 mg/kg, orally) and/or fractionated LDR (0.25 Gy, of the total dose of 0.5 Gy, 1st and 7th day, respectively) on (5 mg/kg, intraperitoneally) cisplatin as a single dose was administered at the 5th day. Serum urea, creatinine and renal kidney injury molecule-1 were measured for the assessment of kidney function. Furthermore, the antioxidant potential in the renal and brain tissues was evaluated through, malondialdehyde and reduced glutathione estimation. Moreover, renal apoptotic markers: AMP-activated protein kinase, lipocalin, B-cell lymphoma 2 associated X protein, B-cell lymphoma 2, P53 and beclin 1 were estimated. UE was evaluated through the determination of serum inflammatory markers: nuclear factor kappa B, tumor-necrosis factor-α and interleukin 1 beta likewise, the cognitive deficits were assessed via forced swimming test, gamma-aminobutyric acid, n-methyl-d-aspartate and neuronal nitric oxide synthases besides AMP-activated protein kinase, light chain 3 and caspase3 levels in rats' cerebella.

KEY FINDINGS

The obtained results revealed a noticeable improvement in the previously mentioned biochemical factors and behavioral tasks that was reinforced by histopathological examination when using the present remedy.

SIGNIFICANCE

metformin and low doses of radiation afforded renoprotection and neuroprotection against cisplatin-induced acute uremic encephalopathy.

Effects of metformin on lipopolysaccharide induced inflammation by activating fibroblast growth factor 21

Lipopolysaccharide (LPS) is a component of the cell wall of Gram-negative bacteria that produces endotoxemia, which may cause septic shock. Metformin (MET) is a widely used hypoglycemic drug that exhibits anti-inflammatory properties. Fibroblast growth factor 21 (FGF21) is an endocrine polypeptide that affects glucose and lipid metabolism, and also possesses anti-inflammatory properties. We investigated the effects of MET and FGF21 on inflammation due to LPS induced endotoxemia in male rats. Animals were divided into five groups: control, LPS, pre-MET LPS, LPS + 1 h MET and LPS + 3 h MET. Serum levels of alanine aminotransferase, aspartate aminotransferase, FGF2, interleukin-10 and tumor necrosis factor alpha were measured. Malondialdehyde, myeloperoxidase and FGF21 levels were measured in liver tissue samples. Histopathology of all groups was assessed using hematoxylin and eosin stained sections. LPS caused severe inflammatory liver damage. MET exhibited a partially protective effect and reduced inflammation significantly. FGF21 is produced in the liver following inflammation and MET may increase its production.

Association between prior metformin therapy and sepsis in diabetes patients: a nationwide sample cohort study

PURPOSE

There have been no large-scale studies on whether metformin therapy might have a potential benefit for lowering mortality. Thus, this study aimed to investigate the association between prior metformin therapy and the development of sepsis as well as the association between prior metformin therapy and 30-day mortality in sepsis patients.

METHODS

We evaluated adult diabetes patients registered in the 2010 sample cohort database of the National Health Insurance Service in South Korea. Diabetes was identified according to the International Classification of Disease-10 diagnostic system (E10-E14). The cohorts were divided into the metformin user group (i.e., those who had been prescribed continuous oral metformin over a period of ≥ 90 days) and the control group (i.e., all other individuals). The primary endpoint was the development of sepsis between 2011 and 2015, and the secondary endpoint was 30-day mortality among diabetes patients diagnosed with sepsis.

RESULTS

In total, 77,337 patients (34,041 in the metformin user group and 43,296 in the control group) were included in the analysis, among whom 2512 patients (3.2%) were diagnosed with sepsis between 2011 and 2015. After propensity score adjustment, metformin use was not significantly associated with both the risk of sepsis (OR: 0.92, 95%CI 0.82-1.03; P = 0.143) and the risk of 30-day mortality after diagnosis of sepsis (OR: 0.94, 95%CI 0.75-1.17; P = 0.571).

CONCLUSIONS

Prior metformin therapy was not significantly associated with the risk of sepsis and 30-day mortality after diagnosis of sepsis among diabetes patients.

Succinate dehydrogenase inhibitor dimethyl malonate alleviates LPS/d-galactosamine-induced acute hepatic damage in mice

In addition to its energy-supplying function, increasing evidence suggests that mitochondria also play crucial roles in the regulation of inflammation. Succinate dehydrogenase is also known as mitochondrial complex II, and inhibition of succinate dehydrogenase by dimethyl malonate has been reported to suppress the production of pro-inflammatory cytokines. In the present study, the potential anti-inflammatory benefits of dimethyl malonate were investigated in a mouse model with LPS/d-galactosamine-induced acute hepatic damage. Male BALB/c mice were injected i.p. with LPS and d-galactosamine to cause liver injury. The degree of liver injury, inflammatory response and oxidative stress and the survival of the experimental animals were determined. The results indicated dimethyl malonate decreased the level of aminotransferases in plasma, alleviated histological abnormalities in liver, inhibited the induction of TNF-α and IL-6 in plasma, suppressed hepatocyte apoptosis and improved the survival of LPS/d-galactosamine-exposed mice. Therefore, inhibition of succinate dehydrogenase by dimethyl malonate significantly alleviated LPS/d-galactosamine-induced hepatic damage, which suggests that succinate dehydrogenase might become a novel target for the intervention of inflammation-based hepatic disorders.

Association of preadmission metformin use and mortality in patients with sepsis and diabetes mellitus: a systematic review and meta-analysis of cohort studies

BACKGROUND

Recent studies have reported that preadmission metformin users had lower mortality than non-metformin users in patients with sepsis and diabetes mellitus; however, these results are still controversial. Therefore, we conducted a systematic review and meta-analysis of published observational cohort data to determine the association between preadmission metformin use and mortality in septic adult patients with diabetes mellitus.

METHODS

The MEDLINE, EMBASE, and Cochrane CENTRAL databases were searched from their inception to September 30, 2018. Cohort studies that evaluated the use of metformin in septic adult patients with diabetes mellitus were included. The quality of outcomes was evaluated using the Newcastle-Ottawa Scale (NOS). The inverse variance method with random effects modelling was used to calculate the pooled odds ratios (ORs) and 95% CIs.

RESULTS

Five observational cohort studies (1282 patients) that were all judged as having a low risk of bias were included. In this meta-analysis, metformin use was associated with a significantly lower mortality rate (OR, 0.59; 95% CI, 0.43-0.79, P = 0.001).

CONCLUSIONS

This meta-analysis indicated an association between metformin use prior to admission and lower mortality in septic adult patients with diabetes mellitus. This finding suggested that the possible effect of metformin should be evaluated in future clinical trials.

Protective Effects of Sesquiterpenoids from the Root of Panax ginseng on Fulminant Liver Injury Induced by Lipopolysaccharide/d-Galactosamine

It is reported that sesquiterpenoids from Panax ginseng (SPG) possess various pharmacological activities, for example, antidepressant, antioxidative, and anti-inflammatory activities. The purpose of this study was to examine the hepatoprotective effects of SPG (2.5 and 10 mg/kg, i.g.) on fulminant liver injury induced by d-galactosamine (d-GalN) and lipopolysaccharide (LPS) and discuss its mechanisms of action. After 24 h of d-GalN (400 mg/kg, i.p.) and LPS (25 μg/kg, i.p.) exposure, the serum levels of alanine transaminase (ALT) and aspartate transaminase (AST), hepatic malondialdehyde (MDA) level, hepatic activities of superoxide dismutase (SOD), catalase (CAT), and glutathione (GSH), and hepatic tissue histology were measured. Expression levels of tumor necrosis factor α (TNF-α) and interleukin-1β (IL-1β) were detected by enzyme-linked immunosorbent assay and real-time polymerase chain reaction. Moreover, the nuclear factor κ-light-chain-enhancer of activated B cell (NF-κB), nuclear factor erythroid 2-related factor 2 (Nrf2), sirtuin type 1 (Sirt 1), and heme oxygenase 1 (HO-1) were determined by western blotting. The results indicated that SPG evidently restrained the increase of serum ALT and AST levels induced by d-GalN/LPS. SPG obviously downregulated TNF-α and IL-1β levels and their mRNA expression in liver. In addition, d-GalN/LPS injection induced severe oxidative stress in liver by boosting the MDA level as well as decreasing CAT, GSH, and SOD capacities, and SPG reversed these changes. Meanwhile, SPG inhibited NF-κB activation induced by d-GalN/LPS and upregulated Sirt 1, Nrf2, and HO-1 expression levels. Therefore, SPG might protect against the fulminant liver injury induced by d-GalN/LPS via inhibiting inflammation and oxidative stress. The protective effect of SPG on fulminant liver injury induced by d-GalN/LPS might be mediated by the Sirt 1/Nrf2/NF-κB signaling pathway. All of these results implied that SPG might be a promising food additive and therapeutic agent for fulminant liver injury.

Maslinic acid protects against lipopolysaccharide/d-galactosamine-induced acute liver injury in mice

Acute liver injury is a life-threatening syndrome that often caused by hepatocyte damage. In this study, we investigated the protective effects of maslinic acid (MA) on lipopolysaccharide (LPS)/d-galactosamine (D-gal)-induced acute liver injury and clarified its mechanism. Mice acute liver injury model was induced by given LPS and D-gal and MA was given intraperitoneally 1 h before LPS and D-gal. Our results showed that MA protected against liver injury by attenuating liver histopathologic changes, serum AST and ALT levels. The increased inflammatory cytokines TNF-α and IL-6 in serum and liver tissues were also inhibited by MA. The level of MDA and the activity of MPO in liver tissues were up-regulated by LPS/D-gal and dose-dependently inhibited by MA. Furthermore, MA attenuated hepatic NF-κB protein expression and increased hepatic Nrf2 and HO-1 protein expression. Taken together, MA offers a protective role against LPS/D-gal-induced liver injury through suppressing NF-κB and activating Nrf2 signaling pathways.

Potential roles of AMP-activated protein kinase in liver regeneration in mice with acute liver injury

Liver regeneration post severe liver injury is crucial for the recovery of hepatic structure and function. The energy sensor AMP‑activated protein kinase (AMPK) has a crucial role in the regulation of nutrition metabolism in addition to other energy‑intensive physiological and pathophysiological processes. Cellular proliferation requires intensive energy and nutrition support, therefore the present study investigated whether AMPK is involved in liver regeneration post carbon tetrachloride (CCl4)‑induced acute hepatic injury. The experimental data indicated that phosphorylation level of AMPK increased 48 h post‑CCl4 exposure, which was accompanied with upregulation of proliferating cell nuclear antigen (PCNA) and recovery of alanine aminotransferase (ALT) level. Pretreatment with the AMPK inhibitor compound C had no obvious effects on ALT elevation in plasma and histological abnormalities in liver 24 h post CCl4 exposure. However, treatment with compound C 24 h post CCl4 exposure significantly suppressed CCl4‑induced AMPK phosphorylation, PCNA expression and ALT recovery. These data suggest that endogenous AMPK was primarily activated at the regeneration stage in mice with CCl4‑induced acute liver injury and may function as a positive regulator in liver regeneration.

Intraportal mesenchymal stem cell transplantation prevents acute liver failure through promoting cell proliferation and inhibiting apoptosis

BACKGROUND

Transplantation of mesenchymal stem cells (MSCs) has been regarded as a potential treatment for acute liver failure (ALF), but the optimal route was unknown. The present study aimed to explore the most effective MSCs transplantation route in a swine ALF model.

METHODS

The swine ALF model induced by intravenous injection of D-Gal was treated by the transplantation of swine MSCs through four routes including intraportal injection (InP group), hepatic intra-arterial injection (AH group), peripheral intravenous injection (PV group) and intrahepatic injection (IH group). The living conditions and survival time were recorded. Blood samples before and after MSCs transplantation were collected for the analysis of hepatic function. The histology of liver injury was interpreted and scored in terminal samples. Hepatic apoptosis was detected by TUNEL assay. Apoptosis and proliferation related protein expressions including cleaved caspase-3, survivin, AKT, phospho-AKT (Ser473), ERK and phospho-ERK (Tyr204) were analyzed by Western blotting.

RESULTS

The average survival time of each group was 10.7+/-1.6 days (InP), 6.0+/-0.9 days (AH), 4.7+/-1.4 days (PV), 4.3+/-0.8 days (IH), respectively, when compared with the average survival time of 3.8+/-0.8 days in the D-Gal group. The survival rates between the InP group and D-Gal group revealed a statistically significant difference (P<0.01). Pathological and biochemical analysis showed that liver damage was the worst in the D-Gal group, while less injury in the InP group. Histopathological scores revealed a significant decrease in the InP group (3.17+/-1.04, P<0.01) and AH group (8.17+/-0.76, P<0.05) as compared with that in the D-Gal group (11.50+/-1.32). The apoptosis rate in the InP group (25.0%+/-3.4%, P<0.01) and AH group (40.5%+/-1.0%, P<0.05) was lower than that in the D-Gal group (70.6%+/-8.5%). The expression of active caspase-3 was inhibited, while the expression of survivin, AKT, phospho-AKT (Ser473), ERK and phospho-ERK (Tyr204) was elevated in the InP group.

CONCLUSIONS

Intraportal injection was superior to other pathways for MSC transplantation. Intraportal MSC transplantation could improve liver function, inhibit apoptosis and prolong the survival time of swine with ALF. The transplanted MSCs may participate in liver regeneration via promoting cell proliferation and suppressing apoptosis during the initial stage of ALF.

Combined mesenchymal stem cell transplantation and interleukin-1 receptor antagonism after partial hepatectomy

AIM

To study the therapeutic effects of mesenchymal stem cells (MSCs) and an interleukin-1 receptor antagonist (IL-1Ra) in acute liver failure.

METHODS

Chinese experimental miniature swine (15 ± 3 kg, 5-8 mo) were obtained from the Laboratory Animal Centre of the Affiliated Drum Tower Hospital of Nanjing University Medical School. Acute liver failure was induced via 85% hepatectomy, and animals were treated by MSC transplantation combined with IL-1Ra injection. Blood samples were collected for hepatic function analysis, and the living conditions and survival time were recorded. Liver injury was histologically analyzed. Hepatic cell regeneration and apoptosis were studied by Ki67 immunohistochemistry and terminal deoxynucleotidyl transferase dUTP nick end labeling, respectively. The levels of protein kinase B and nuclear factor-κB expression were analyzed by Western blotting.

RESULTS

MSCs were infected with a lentivirus for expression of green fluorescent protein (GFP) for subsequent identification; 97.3% of the MSCs were positive for GFP as assessed by flow cytometry. Additional flow cytometric analysis of cell surface marker expression demonstrated that > 90% of GFP-expressing MSCs were also positive for CD29, CD44, and CD90, indicating that most of these cells expressed typical markers of MSCs, and the population of MSCs was almost pure. Transplantation of MSCs in combination with 2 mg/kg IL-1Ra therapy significantly improved survival time compared to the acute liver failure model group (35.3 ± 6.7 d vs 17.3 ± 5.5 d, P < 0.05). Combined therapy also promoted improvement in serum inflammatory cytokines and biochemical conditions. The observed hepatic histopathologic score was significantly lower in the group with combined therapy than in the model group (3.50 ± 0.87 vs 8.17 ± 1.26, P < 0.01). In addition, liver cell apoptosis in the combined therapy group was significantly inhibited (18.1 ± 2.1% vs 70.8 ± 3.7%, P < 0.01), and hepatic cell regeneration increased. A significant increase in protein kinase B expression and decrease in nuclear factor-κB expression were observed (P < 0.01), which supports their important roles in liver regeneration.

CONCLUSION

MSCs and IL-1Ra had a synergistic effect in liver regeneration via regulation of inflammation and apoptotic signaling.

Effect of Cichorium intybus L. on the expression of hepatic NF-κB and IKKβ and serum TNF-α in STZ- and STZ+ niacinamide-induced diabetes in rats

BACKGROUND

Inflammation is an early event in the development of diabetes type 2 (T2D). Cichorium intybus L. (chicory) possesses anti-inflammatory action. We compared the anti-inflammatory aspect of aqueous chicory seed extract (CSE) in early and late stage T2D in rats.

METHODS

Wistar albino rats were divided into nine final groups (n = 6). Three main groups consisted of non-diabetic (Control), early stage diabetes (ET2D; niacinamide/streptozotocin, i.e., NIA/STZ), and late stage diabetes (LT2D; STZ). Within each main group, a subgroup was treated with CSE (125 mg/kg; i.p.); within each diabetic group (STZ and NIA/STZ) a subgroup received metformin (100 mg/kg; i.p.); another subgroup in STZ group received aspirin (120 mg/kg; oral). After 21 days, fasting blood glucose (FBS), insulin, and TNF-α level were measured in serum; IKKβ and NF-κB (p65) mRNA and protein expression were evaluated by real time PCR and Western blotting; p65 DNA binding activity was determined by ELISA, in liver tissue.

RESULTS

The mRNA and protein expression levels of IKKβ, and P65 genes increased in both stages of T2D (p < 0.01); CSE decreased their expression (p < 0.001, mRNAs; p < 0.05, proteins). The increased DNA-binding capacity of NF-κB (p < 0.0001) in diabetes was lowered by CSE (p < 0.001). The effect of CSE was limited to ET2D requiring insulin.

CONCLUSIONS

The anti-inflammatory action of CSE is due to a direct modulation of cytokine expression. The dependency of chicory action on the presence of insulin indicates its usefulness in the early stages of diabetes and for the purpose of preventing and delaying diabetes onset.

Is Liver Enzyme Release Really Associated with Cell Necrosis Induced by Oxidant Stress?

Hepatic diseases are a major concern worldwide. Increased specific plasma enzyme activities are considered diagnostic features for liver diseases, since enzymes are released into the blood compartment following the deterioration of the organ. Release of liver mitochondrial enzymes is considered strong evidence for hepatic necrosis, which is associated with an increased production of ROS, often leading to greater hepatic lipid peroxidation. Lipotoxic mediators and intracellular signals activated Kupffer cells, which provides evidence strongly suggesting the participation of oxidant stress in acute liver damage, inducing the progression of liver injury to chronic liver damage. Elevated transaminase activities are considered as an index marker of hepatotoxicity, linked to oxidant stress. However, a drastic increase of serum activities of liver enzyme markers ought not necessarily to reflect liver cell death. In fact, increased serum levels of cytoplasmic enzymes have readily been observed after partial hepatectomy (PH) in the regenerating liver of rats. In this regard, we are now showing that in vitro modifications of the oxidant status affect differentially the release of liver enzymes, indicating that this release is a strictly controlled event and not directly related to the onset of oxidant stress of the liver.

Metformin suppresses intrahepatic coagulation activation in mice with lipopolysaccharide/D‑galactosamine‑induced fulminant hepatitis

Metformin is a widely‑used antidiabetic drug with hypoglycemic activity and previously described anti‑inflammatory properties. Previous studies have demonstrated that metformin attenuates endotoxic hepatitis, however the mechanisms remain unclear. Inflammation and coagulation are closely associated pathological processes, therefore the potential effects of metformin on key steps in activation of the coagulation system were further investigated in endotoxic hepatitis induced by lipopolysaccharide/D‑galactosamine (LPS/D‑Gal). The current study demonstrated that treatment with metformin significantly suppressed the upregulation of tissue factor and plasminogen activator inhibitor‑1 in LPS/D‑Gal‑exposed mice. In addition, a reduction in the expression of interleukin 6 and inhibition of nuclear translocation of nuclear factor‑κB were observed. These data indicate that the LPS/D‑Gal‑induced elevation of the stable protein level of hypoxia inducible factor 1α, the mRNA level of erythropoietin, vascular endothelial growth factor and matrix metalloproteinase‑3, and the hepatic level of lactic acid were also suppressed by metformin. The current study indicates that the suppressive effects of metformin on inflammation‑induced coagulation may be an additional mechanism underlying the hepatoprotective effects of metformin in mice with LPS/D‑Gal‑induced fulminant hepatitis.

Early treatment with metformin induces resistance against tumor growth in adult rats

It is known that antidiabetic drug metformin, which is used worldwide, has anti-cancer effects and can be used to prevent cancer growth. We tested the hypothesis that tumor cell growth can be inhibited by early treatment with metformin. For this purpose, adult rats chronically treated with metformin in adolescence or in adulthood were inoculated with Walker 256 carcinoma cells. Adult rats that were treated with metformin during adolescence presented inhibition of tumor growth, and animals that were treated during adult life did not demonstrate any changes in tumor growth. Although we do not have data to disclose a molecular mechanism to the preventive metformin effect, we present, for the first time, results showing that cancer growth in adult life is dependent on early life intervention, thus supporting a new therapeutic prevention for cancer.

Antidiabetic drug metformin is effective on the metabolism of asymmetric dimethylarginine in experimental liver injury

AIMS

We aimed to investigate the pharmacological efficiency of metformin on asymmetric dimethylarginine (ADMA) metabolism in inflammation caused by the lipopolysaccharide (LPS)/D-galactosamine (D-GalN) treatment.

METHODS

Adult Sprague-Dawley rats were injected LPS/D-GalN intraperitoneally. One half of the animals was injected metformin (250 mg kg(-1) body mass for one week) prior to LPS/D-GalN treatment. Six hours after the LPS/D-GalN injection, livers were removed, and used for the measurements of dimethylarginine dimethylaminohydrolase (DDAH) and myeloperoxidase (MPO) activities, glutathione (GSH), ADMA and arginine levels. Liver tissues were examined histopathologically. The Kruskal-Wallis (posthoc Mann-Whitney U) test was used for the statistics. LPS/D-GalN injections caused liver injury as evidenced by the activities of aminotransferases and arginase. GSH level and DDAH activity were decreased in the liver. Metformin pretreatment alleviated the activity of serum enzymes, and attenuated histopathological lesions caused by LPS/D-GalN injections. LPS/D-GalN-induced inflammation, as confirmed by the increased MPO activity, created an asymmetrical distribution of arginine and ADMA between the tissue and plasma. Metformin decreased tissue ADMA level while it restored the DDAH activity and GSH.

CONCLUSION

Our findings showed that metformin administration for one week has a potency to protect liver through regulating ADMA metabolism in LPS/D-GalN-induced injury.

Potential role of catalase in mice with lipopolysaccharide/D-galactosamine-induced fulminant liver injury

AIM

Lipopolysaccharide (LPS)-induced liver injury in D-galactosamine (D-Gal)-sensitized mice is a well-established animal model widely used in exploring the pathogenesis of fulminant hepatitis. Increasing evidence has indicated that reactive oxygen species (ROS)-induced oxidative injury may be involved in LPS/D-Gal-induced hepatitis. Catalase (CAT) is a major antioxidant enzyme while aminotriazole (ATZ) is commonly used as a CAT inhibitor. In the present study, the effects of ATZ on LPS/D-Gal-induced liver injury were investigated.

METHODS

Fuliminant liver injury was induced by intraperitoneal injection of LPS combined with D-Gal, ATZ was administrated 0.5 h prior to LPS/D-Gal challenge. The degree of liver injury, the level of hepatic oxidative stress, the grade of hepatic apoptosis and the survival of experimental animals were determined.

RESULTS

Our experimental data showed that treatment with ATZ significantly enhanced LPS/D-Gal-induced elevation of serum aspartate transaminase (AST) and alanine transaminase (ALT), exacerbated the hepatic histopathological abnormality and decreased the survival rate of experimental animals. ATZ inhibited the activity of CAT, increased the content of H2 O2 and the levels of malondialdehyde (MDA) in liver tissues. In addition, treatment with ATZ also enhanced LPS/D-Gal-induced hepatic apoptosis as evidenced by increased caspases activities in liver tissues and increased number of terminal deoxynucleotidyl transferase dUTP nick end labeling positive cells in liver sections.

CONCLUSION

These findings suggested that CAT might be involved in the progression of LPS/D-Gal-induced fulminant liver injury.

Effects of glycemic control on glucose utilization and mitochondrial respiration during resuscitated murine septic shock

Background

This study aims to test the hypothesis whether lowering glycemia improves mitochondrial function and thereby attenuates apoptotic cell death during resuscitated murine septic shock.

Methods

Immediately and 6 h after cecal ligation and puncture (CLP), mice randomly received either vehicle or the anti-diabetic drug EMD008 (100 μg · g^-1). At 15 h post CLP, mice were anesthetized, mechanically ventilated, instrumented and rendered normo- or hyperglycemic (target glycemia 100 ± 20 and 180 ± 50 mg · dL^-1, respectively) by infusing stable, non-radioactive isotope-labeled ¹³C₆-glucose. Target hemodynamics was achieved by colloid fluid resuscitation and continuous i.v. noradrenaline, and mechanical ventilation was titrated according to blood gases and pulmonary compliance measurements. Gluconeogenesis and glucose oxidation were derived from blood and expiratory glucose and ¹³CO₂ isotope enrichments, respectively; mathematical modeling allowed analyzing isotope data for glucose uptake as a function of glycemia. Postmortem liver tissue was analyzed for HO-1, AMPK, caspase-3, and Bax (western blotting) expression as well as for mitochondrial respiratory activity (high-resolution respirometry).

Results

Hyperglycemia lowered mitochondrial respiratory capacity; EMD008 treatment was associated with increased mitochondrial respiration. Hyperglycemia decreased AMPK phosphorylation, and EMD008 attenuated both this effect as well as the expression of activated caspase-3 and Bax. During hyperglycemia EMD008 increased HO-1 expression. During hyperglycemia, maximal mitochondrial oxidative phosphorylation rate was directly related to HO-1 expression, while it was unrelated to AMPK activation. According to the mathematical modeling, EMD008 increased the slope of glucose uptake plotted as a function of glycemia.

Conclusions

During resuscitated, polymicrobial, murine septic shock, glycemic control either by reducing glucose infusion rates or EMD008 improved glucose uptake and thereby liver tissue mitochondrial respiratory activity. EMD008 effects were more pronounced during hyperglycemia and coincided with attenuated markers of apoptosis. The effects of glucose control were at least in part due to the up-regulation of HO-1 and activation of AMPK.

Electronic supplementary material

The online version of this article (doi:10.1186/2197-425X-2-19) contains supplementary material, which is available to authorized users.

Safety of the intravenous administration of neurotensin-polyplex nanoparticles in BALB/c mice

Neurotensin (NTS)-polyplex is a gene nanocarrier that has potential nanomedicine-based applications for the treatment of Parkinson's disease and cancers of cells expressing NTS receptor type 1. We assessed the acute inflammatory response to NTS-polyplex carrying a reporter gene in BALB/c mice. The intravenous injection of NTS-polyplex caused the specific expression of the reporter gene in gastrointestinal cells. Six hours after an intravenous injection of propidium iodide labeled-NTS-polyplex, fluorescent spots were located in the cells of the organs with a mononuclear phagocyte system, suggesting NTS-polyplex clearance. In contrast to lipopolysaccharide and carbon tetrachloride, NTS-polyplex did not increase the serum levels of tumor necrosis factor alpha, interleukin (IL)-1β, IL-6, bilirubin, aspartate transaminase, and alanine transaminase. NTS-polyplex increased the levels of serum amyloid A and alkaline phosphatase, but these levels normalized after 24 h. Compared to carrageenan, the local injection of NTS-polyplex did not produce inflammation. Our results support the safety of NTS-polyplex.

FROM THE CLINICAL EDITOR

This study focuses on the safety of neurotensin (NTS)-polyplex, a gene nanocarrier that has potential in the treatment of Parkinson's disease and cancers of cells expressing NTS receptor type 1. NTS polyplex demonstrates a better safety profile compared with carrageenan, lipopolysaccharide, and carbon tetrachloride in a murine model.

Metformin aggravates immune-mediated liver injury in mice

Hepatotoxicity of the antidiabetic drug metformin has been reported, but the underlying mechanisms remain unclear. We here investigated the effect of metformin in immune-mediated liver damage. While not hepatotoxic alone, metformin (200 mg/kg) aggravated concanavalin A (Con A, 12 mg/kg)-induced hepatitis, an experimental model of T cell-mediated liver injury, in both relatively resistant BALB/c and highly susceptible C57Bl/6 mice. Metformin + Con A-treated mice had elevated serum levels of pro-inflammatory cytokines TNF-α and IFN-γ, accompanied by a massive mononuclear cell infiltration in the liver. This was associated with the higher numbers of CD4(+) T cells producing TNF-α, IFN-γ and IL-17, CD4(+) T cells expressing chemokine receptor CXCR3 and activation marker CD27, CD4(+)CD62L(-)CCR7(-) and CD8(+)CD62L(-)CCR7(-) effector memory cells, IFN-γ producing NK cells, IL-4 and IL-17 producing NKT cells and IL-12 producing macrophages/dendritic cells. The percentage of CD4(+)CXCR3(+)Tbet(+)IL-10(+) and CD4(+)CD69(+)CD25(-) regulatory T cells was reduced. Metformin stimulated inducible nitric oxide synthase (iNOS) expression in the liver and spleen, and genetic deletion of iNOS attenuated the hepatotoxicity of metformin. Metformin increased the autophagic light chain 3 conversion and mRNA expression of important autophagy-inducing (beclin-1, Atg5 and GABARAP) and pro-apoptotic (p21, p27, Puma, Noxa, Bax, Bad, Bak1, Bim and Apaf1), but not anti-apoptotic molecules (Bcl-xL, survivin and XIAP), which correlated with the apoptotic caspase-3/PARP cleavage in the liver. The autophagy inhibitor chloroquine (20 mg/kg) prevented liver injury and apoptotic changes induced by metformin. Therefore, metformin aggravates immune-mediated hepatitis by promoting autophagy and activation of immune cells, affecting effector, as well as liver-specific regulatory T cells and iNOS expression.

Metformin--mode of action and clinical implications for diabetes and cancer

Metformin has been the mainstay of therapy for diabetes mellitus for many years; however, the mechanistic aspects of metformin action remained ill-defined. Recent advances revealed that this drug, in addition to its glucose-lowering action, might be promising for specifically targeting metabolic differences between normal and abnormal metabolic signalling. The knowledge gained from dissecting the principal mechanisms by which metformin works can help us to develop novel treatments. The centre of metformin's mechanism of action is the alteration of the energy metabolism of the cell. Metformin exerts its prevailing, glucose-lowering effect by inhibiting hepatic gluconeogenesis and opposing the action of glucagon. The inhibition of mitochondrial complex I results in defective cAMP and protein kinase A signalling in response to glucagon. Stimulation of 5'-AMP-activated protein kinase, although dispensable for the glucose-lowering effect of metformin, confers insulin sensitivity, mainly by modulating lipid metabolism. Metformin might influence tumourigenesis, both indirectly, through the systemic reduction of insulin levels, and directly, via the induction of energetic stress; however, these effects require further investigation. Here, we discuss the updated understanding of the antigluconeogenic action of metformin in the liver and the implications of the discoveries of metformin targets for the treatment of diabetes mellitus and cancer.

Protective effects of garcinol in mice with lipopolysaccharide/D-galactosamine-induced apoptotic liver injury

Garcinol is a polyisoprenylated benzophenone derivative of Garcinia indica. Recent researches have revealed the antioxidant, anticancer and anti-inflammatory properties of garcinol. In the present study, the pharmacological effects of garcinol in lipopolysaccharide (LPS)-induced hepatic injury in D-galactosamine (D-Gal)-sensitized mice were investigated. We found that treatment with garcinol significantly decreased serum ALT and AST levels in LPS/D-Gal-exposed mice. These were accomplished with improved histological alterations in liver sections and reduced malondialdehyde (MDA) content in liver homogenates. Garcinol significantly reduced the acetylation level of NF-κB, but it had no obvious effects on the elevation of TNF-α or IL-6 in plasma or liver tissue. Garcinol significantly attenuated LPS/D-Gal-induced hepatic apoptosis as evidenced by reduced number of TUNEL-positive cells in liver sections. Our experiments also showed that garcinol markedly suppressed the cleavage of caspase-3 and significantly decreased the activities of caspase-3, -8, and -9 in liver tissues. In addition, garcinol obviously reduced the induction of Bax but did not alter the level of Bcl-2. These results indicated that garcinol might provide protective benefits in LPS/D-Gal-induced liver injury through suppressing apoptosis.

Hepatic progenitor cells express SerpinB3

Background

In the setting of liver injury hepatic progenitor cells are activated, counterbalancing the inhibited regenerative capacity of mature hepatocytes. Chronic activation of this compartment may give rise to a subset of liver tumours with poor prognosis. SerpinB3, a serpin over-expressed in injured liver and in primary liver cancer, has been shown to induce apoptosis resistance, epithelial to mesenchymal transition and to increase TGF-beta and Myc expression. Aim of the present study was to explore the presence of SerpinB3 in hepatic progenitor cells in human livers and in a mouse model of liver stem/progenitor cell activation.

Hepatic progenitor cells were analysed in foetal and adult livers at protein and transcriptional levels. To induce experimental activation of the liver stem/progenitor compartment, C57BL/6J mice were injected with lipopolysaccharide plus D-galactosamine and were sacrificed at different time points. Liver cDNA was amplified using specific primers for mouse-homologous SerpinB3 isoforms and automatically sequenced.

Results

The presence of SerpinB3 in the progenitor cell compartment was detected in sorted human foetal and adult epithelial cell adhesion molecule (EpCAM) positive liver cells. By immunohistochemistry SerpinB3 was found in human cirrhotic livers in portal areas with progenitor cell activation showing ductular proliferation. CK-7, CK-19, EpCAM and CD-90 positive cell were also positive for SerpinB3. In the animal model, time course analysis in liver specimens revealed a progressive increase of SerpinB3 and a parallel decrease of activated caspase 3, which was barely detectable at 20 hours. Transcription analysis confirmed the presence of SerpinB3-homologous only in the liver of injured mice and sequence analysis proved its belonging to mouse Serpinb3b.

Conclusion

SerpinB3 is highly expressed in hepatic stem/progenitor cell compartment of both foetal and adult livers.

Metformin Down-regulates TNF-α Secretion via Suppression of Scavenger Receptors in Macrophages

Obesity is consistently increasing in prevalence and can trigger insulin resistance and type 2 diabetes. Many lines of evidence have shown that macrophages play a major role in inflammation associated with obesity. This study was conducted to determine metformin, a widely prescribed drug for type 2 diabetes, would regulate inflammation through down-regulation of scavenger receptors in macrophages from obesity-induced type 2 diabetes. RAW 264.7 cells and peritoneal macrophages were stimulated with LPS to induce inflammation, and C57BL/6N mice were fed a high-fat diet to generate obesity-induced type 2 diabetes mice. Metformin reduced the production of NO, PGE₂ and pro-inflammatory cytokines (IL-1β, IL-6 and TNF-α) through down-regulation of NF-κB translocation in macrophages in a dose-dependent manner. On the other hand, the protein expressions of anti-inflammatory cytokines, IL-4 and IL-10, were enhanced or maintained by metformin. Also, metformin suppressed secretion of TNF-α and reduced the protein and mRNA expression of TNF-α in obese mice as well as in macrophages. The expression of scavenger receptors, CD36 and SR-A, were attenuated by metformin in macrophages and obese mice. These results suggest that metformin may attenuate inflammatory responses by suppressing the production of TNF-α and the expressions of scavenger receptors.

Metformin: the hidden chronicles of a magic drug

Metformin, a biguanide is well known treatment for type 2 diabetes mellitus that has diverse mechanism of actions. Various studies have elucidated the role of this drug in different pathologies. The well-known United Kingdom Prospective Diabetic Study (UKPDS) has observed its survival benefits in a large cohort of individuals. Data has been conclusive that metformin also has beneficial role in lipid disorders as it improves the markers of metabolic syndrome. Studies have also shown the beneficial roles in antipsychotic induced weight gain as well as HIV lipodystrophy syndrome. Evidence is accumulating that metformin also improves the fertility in females with Polycystic Ovarian Syndrome (PCOS). It also delays aging and is effective in aging related disorders and is equally effective in inflammation related disorders at least in different rodent studies. Metformin's major effect has been shown in various cancers ranging from solid to hematological malignancies. Researchers are working to reveal more benefits of this magic drug but it remains an unexplored territory for the medical community.